The invention relates to well screens and to the slips used to assist in the placement of a long column of separate screen segments in a well. A slip is a device used in the oil well drilling industry to suspend a column of screen in the well. It is used to hold the column of screen segments already in the well as each additional segment is threaded to it. A conventional slip consists of two or three circumferential steel sections that are hinged together. The sections are wedge shaped and have a serrated gripping surface that digs into and frictionally engages the screen jacket portion of the screen segment. Handles are attached to each section and are used for inserting and removing the slip. In operation, a screen segment is lowered into a circular fixture called a bowl. When all but a few feet of the screen are in the well, the slip is placed between the screen jacket and the bowl. As the screen is lowered more, the slip wedges between the screen and bowl and holds the column in place. Another section of screen is then raised above the column and the coupling is made. The column is then raised slightly to relieve the pressure on the slip. The slip is pulled away from the screen and the next length of screen is lowered into the well. The sections of screen are added on until the required amount of screen has been lowered into the well.
Due to the wedge shape of the slip sections and their serrated gripping surfaces, there is a considerable radial pressure applied to the screen jacket surface which can damage it by deforming the wires and thus changing the slot openings. Furthermore, the conventional slips are quite heavy and must be lifted into and out of the bowl every time a new segment of screen is added. Also, since the pipe joint being completed is quite close to the bowl, considerable bending and stooping by the drilling crew is necessary. When the screen jacket is slightly deformed and one or more of its slots are enlarged, the liquid flowing through the screen will tend to be concentrated in the enlarged slot. This increased flow will permit abrasive particles in the liquid to rapidly wear the slot even wider and the screen's useful life will be a small fraction of what it would be with slots having a constant width.